Re: [PATCH RFC 07/77] PCI/MSI: Re-design MSI/MSI-X interrupts enablement pattern

Alexander Gordeev
2013-10-08T07:48:26Z

On Mon, Oct 07, 2013 at 02:17:49PM -0400, Tejun Heo wrote:
> Hello,
>
> On Wed, Oct 02, 2013 at 12:48:23PM +0200, Alexander Gordeev wrote:
> > +static int foo_driver_enable_msi(struct foo_adapter *adapter, int nvec)
> > +{
> > + rc = pci_get_msi_cap(adapter->pdev);
> > + if (rc < 0)
> > + return rc;
> > +
> > + nvec = min(nvec, rc);
> > + if (nvec < FOO_DRIVER_MINIMUM_NVEC) {
> > + return -ENOSPC;
> > +
> > + rc = pci_enable_msi_block(adapter->pdev, nvec);
> > + return rc;
> > +}
>
> If there are many which duplicate the above pattern, it'd probably be
> worthwhile to provide a helper? It's usually a good idea to reduce
> the amount of boilerplate code in drivers.

I wanted to limit discussion in v1 to as little changes as possible.
I 'planned' those helper(s) for a separate effort if/when the most
important change is accepted and soaked a bit.

> > @@ -975,7 +951,7 @@ int pci_enable_msix(struct pci_dev *dev, struct msix_entry *entries, int nvec)
> > if (nr_entries < 0)
> > return nr_entries;
> > if (nvec > nr_entries)
> > - return nr_entries;
> > + return -EINVAL;
> >
> > /* Check for any invalid entries */
> > for (i = 0; i < nvec; i++) {
>
> If we do things this way, it breaks all drivers using this interface
> until they're converted, right?

Right. And the rest of the series does it.

> Also, it probably isn't the best idea
> to flip the behavior like this as this can go completely unnoticed (no
> compiler warning or anything, the same function just behaves
> differently). Maybe it'd be a better idea to introduce a simpler
> interface that most can be converted to?

Well, an *other* interface is a good idea. What do you mean with the
simpler here?

> tejun

--
Regards,
Alexander Gordeev
agordeev@redhat.com